riscos-romtools

Tools for creating customised RISC OS 3 ROM images and "5th-column" Extension ROMs.

Phil Pemberton, philpem@gmail.com

If you do anything cool with this, please send me an email!

Requirements

You will need the "srecord" tools.

The Python scripts require Python 3. mkrom.py also requires the Python 3 yaml module.

TODO

• Extend mkrom.py to create Podule ROMs.

Tools included

• RISC OS ROM tools
  • checksum (C program): Checks the RISC OS ROM checksum trailer (Additive sum and CRCs) and reports on its correctness.
  • patchsum (C program): Fixes the ROM header (ROM length word) and trailer (checksums).
  • merge.sh: Convert a 4-file emulator-format RISC OS ROM image into a single file.
  • pad2mb.sh, pad4mb.sh: Pad a ROM image to 4MB without fixing checksums
  • stripe.sh: Take a 2MB or 4MB ROM image and create a High and Low stripe image which may be programmed into a pair of M27C160-100 EPROMs.
• 5th-Column and Podule ROM tools
  • podrom.c (C program): Extract modules and data areas from a 5th Column or Podule ROM
  • mkrom.py: Creates a 5th Column ROM based on a YAML configuration file.
    • With minor changes, it could also be used to create Podule ROMs.

Typical workflow (RISC OS ROM)

• Generate a modified RISC OS ROM using qUE's tools and Flibble's tutorial
• Use pad4mb.sh to pad it to 4MB
• Use patchsum to fix the checksum and ROM size header
• Test it in Arculator
• Use stripe.sh to create images to program into 16-bit EPROMs
• Program some EPROMs and test them

4MB RISC OS ROM image generally don't work in ARM250-based machines. For reasons unknown, the ROM self test always fails.

When using a 4MB ROM, it will not be possible to use a POST Box to view the self-test output on any machine which uses LA<21> for the TESTREQ function. This includes the ARM250 machines, e.g. A3010, A3020 and A4000.

Typical workflow (5th Column ROM)

• (Optional) Use podrom to extract the modules you need from a Podule or 5th Column ROM. (useful for Wizzo).
• Edit config.yml to list the modules you want in your final ROM.
• Run mkrom.py to build a 5th Column ROM.
• Assuming your 5th Column ROM is 64k in size:
  • Take a RISC OS 3.11 ROM dump
  • Append (2MB - 64k) of filler bytes (e.g. 0xFF)
  • Append your 5th Column ROM image
• Use stripe.sh to generate the striped images
• Program some EPROMs!

EPROM compatibility

The RISC OS 3.11 ROM (2MB) may be programmed into a pair of STMicroelectronics M27C800-100 DIP-package 42-pin EPROMs.

If a custom ROM is created which requires a 4MB ROM, a pair of STMicroelectronics M27C160-100 DIP-package 42-pin EPROMs may be used.